The invention relates to turbine engine parts forming compressor stators or turbine nozzles. The field of application of the invention is in particular that of aeroengines. Nevertheless, the invention is also applicable to other turbine engines, e.g. industrial gas turbines.
In turbine engines, the compressor and turbine modules comprise rotary wheels alternating with stators in compressors or with nozzles in turbines.
A traditional compressor stator in widespread use comprises a plurality of guide vanes, e.g. fastened by welding to an outer ring that has a structural function and that defines the outside of the air flow passage. On the inside, the air flow passage is defined by a non-structural inner shroud. The outer ring, the vanes, and the inner shroud are typically made of metal.
A conventional turbine nozzle is commonly made up of a plurality of metal sectors, each obtained as a single part by casting and each comprising an outer shroud sector defining the outside of the gas flow passage, an inner shroud sector defining the inside of the gas flow passage, and vanes connecting together the outer and inner shroud sectors.
The use of composite materials comprising fiber reinforcement densified by a matrix has already been proposed for various turbine engine parts, and in particular rotary wheel airfoils, turbine rings, turbine nozzle elements, or after-body elements. For parts that are exposed in operation to high temperatures, it is recommended to use a ceramic matrix composite (CMC) material. The fabrication of such parts comprises making a fiber preform forming the fiber reinforcement of the composite material and having a shape close to the shape of the part that is to be fabricated, and then densifying the fiber preform with a matrix. The fiber preform may be obtained using various textile processes, in particular shaping a fiber blank that is made by multilayer or three-dimensional weaving.
Such composite material parts are remarkable in that they present good mechanical properties, at least comparable to those of similar metal parts, but associated with lower weight, and when CMC materials are used, these parts conserve their mechanical properties at very high temperatures and they are therefore suitable for use when it is desired to reach the highest possible operating temperatures for turbine engines in order to improve efficiency and reduce polluting emissions.
Thus, document EP 1 526 285 describes making a fan blade by densifying a fiber preform obtained by three-dimensional weaving with an organic matrix. Documents WO 2010/061140 and WO 2010/103213 respectively describe making blades with incorporated inner and/or outer platforms and turbine ring sectors out of CMC material using fiber blanks made by multilayer weaving.
Document WO 2010/146288 describes a CMC turbine nozzle element made up of inner shroud sectors and of outer shroud sectors together with vanes extending between the sectors and obtained by a multilayer woven fiber blank with continuity of the fiber reinforcement throughout the volume of the nozzle element. The fiber reinforcement includes yarns that extend continuously along two vanes by passing via the inner shroud sector or the outer shroud sector, but said yarns are subsequently interrupted. In addition, there is no continuity of the yarns of the fiber reinforcement in the circumferential direction along each of the inner and outer shroud sectors.
Document WO 91/15357 describes folding a knitted fiber blank concertina-wise so as to make a nozzle sector having a plurality of vanes. Nevertheless, the folding is such that it likewise does not make it possible to ensure continuity of the fiber reinforcement in the circumferential direction along the outer shroud sector and along the inner shroud sector.